Silica organo sol friction treatment composition and method of application



United States Patent 3,547,663 SILICA ORGANO SOL FRICTION TREAT- MENT COMPOSITION AND METHOD OF APPLICATION Lawrence L. Bott, Oak Park, Ill., assignor to Nalco Chemical Company, Chicago, Ill., a corporation of Delaware No Drawing. Filed Dec. 1, 1967, Ser. No. 687,125 Int. Cl. C09k 3/14, 3/18 US. Cl. 10636 8 Claims ABSTRACT OF THE DISCLOSURE This invention is directed to a method of improving the coefiicient of friction between contacting metal surfaces moving one with respect to the other. This result is achieved by treating at least one of said surfaces with a silica organo sol having as its continuous phase a lower aliphatic liquified hydrocarbon gas and as its dispersed phase at least 0.1% by weight of hydrophobic, dense, discrete surface esterified silica particles. This invention also is directed to novel organo silica sols wherein the continuous phase is a lower aliphatic liquified hydrocarbon gas and the dispersed phase is an esterified colloidal silica composed of hydrophobic, dense, discrete surface esterified silica particles.

INTRODUCTION This invention relates to a new, improved adhesion treatment for metal surfaces. More particularly it relates to a method and composition for increasing the coefficient of friction at a very fast rate between metal surfaces capab e of motion one with respect to the other. The invention is especially concerned with the provision of chemical means for preventing wheel slippage between locomotive wheels and rails. However, in its broader aspects the invention contemplates the improvement of frictional contact between metal surfaces which are susceptible of slippage one with respect to the other, as, for example, the slippage which occurs between a shaft and a sheave, gear or pinion frictionally mounted on said shaft.

The past several decades have produced railway locomotives possessing great power and weight, thus enabling long, heavily-laden trains to be pulled by single engines. With the advent of the extremely heavy locomotive it was felt that driving wheel slip would be eliminated. It was soon discovered, however, that the increased static weight carried on the driving wheels did not solve the problem to any great extent. Track sanding techniques were developed but this only partially alleviated the condition. Wheel slippage has proven to be an erratic condition which has not in all cases been satisfactorily explained.

In one explanation of the problem, rail slip is said to result from a tough invisible oxidized oil film on the wear band of the rail. Traffic and heat destroy this film and high adhesion results. When a light rain occurs or when the rails reach the dew point, as the result of the relatively high humidity, a water film forms across the wear band where it may contact oil deposits on the edge of a rail with the result that a film of oil creeps through and replaces the water film. The oil deposits on the rail sides act as the transporting agent. The oil deposits on the rail come from journal box oil leakage by way of the outside face and outer portion of the tread of the car wheels. There are other sources of contamination such as road crossings, rail lubricators, and the like.

The importance of solving the problem is strikingly il lustrated when it is realized that only 15% of the engines weight can be utilized as tractive force when the rails are greasy and moist, and 30% when the rails are clean, dry

3,547,663 Patented Dec. 15, 1970 "Ice and sanded. Even a small improvement in these figures, as expressed in the terms of increased coefficient of friction, would enable railway locomotives to operate more efiiciently and economically as well as providing improved braking for railway locomotives and rolling stock.

Another instance where it is desirable to improve the frictional contact between two metal surfaces capable of motion one with respect to the other is where a gear or pinion is frictionally mounted on a shaft. Obviously, if slippage occurs between the gear or pinion and the shaft the efliciency of the particular operation in question is reduced or the device may even become inoperable.

It is now known that certain finely divided siliceous compositions as well as other finely divided materials are valuable treatments for improving the coefficient of friction between metal surfaces which are capable of motion one with respect to the other. Typical siliceous type treat; ment comprise finely divided silica powders, aqueous colloidal silica sols used either alone or dispersed in wateralcohol systems, silica pastes, formed from aqueous colloidal silica sols, finely divided alumino-silicates and the like. The use of such materials as frictionizing treatments is described in the following US. Pats: 2,877,716; 2,819,- 681; 2,787,968. 2,787,967; 2,787,966 and 2,787,965.

All of the materials described in the above patents have demonstrated remarkable effectiveness in improving the frictional contact between moving metal surfaces. Laboratory experimentation as well as extensive tests in the treating of railway car wheels and tracks, however, has shown that the maximum increase in friction only is obtained when the silica or siliceous materials contained in such products are dry. Since finely divided silicas are most conveniently applied in the form of a liquid or paste it is, therefore, necessary to have such materials dry in order to obtain the maximum effectiveness when used as frictionizing materials.

One attempt to overcome this deficiency of the liquid suspended finely divided silicas is to apply them in the form of a dust. While this has presented a partial solution to the problem it is not entirely satisfactory since the finely divided silica dusts are so light and fluffy they are diflicult to adhere to the metal surfaces when applied in small quantities. Since many of the finely divided silicas are in the form of fume-type dusts they tend to be blown about by the atmosphere, thereby requiring excessive amounts to be applied to metal surfaces if good frictional effects are to be achieved.

It would be beneficial if a frictionizing material were available which could be applied in liquid form to moving metal surfaces and would develop maximum coefiicients of friction within relatively short periods of time after application. Also of benefit would be a product which would furnish relatively large quantities of silica contained in a liquid form which could be applied in metered amounts to railway car wheels and/ or tracks to cause immediate increase in the coefiicient of friction using small economical dosages of the frictionizing chemical.

OBJECTS It, therefore, is an object of the invention to provide improved frictionizing treatment for increasing the coefficient of friction between metal surfaces that tend to move one with respect to the other.

It is also an object of the invention to provide a siliceous-type frictionizing material which is in the form of a colloidal suspension which may be applied to moving metal surfaces and will rapidly develop a maximum coefficient of friction at an extremely rapid rate.

As indicated in the Abstract of the Disclosure a specific object of the invention is the provision of new and novel organo-silica sols. Other objects will appear hereafter.

3 THE INVENTION In accordance with the invention it has been found that the coefficient of friction between contacting metal surfaces capable of moving one with respect to the other may be improved by applying to at least one of the contacting surfaces a silica organo sol, said organo sol having as its continuous phase a lower aliphatic liquified hydrocarbon gas and as the dispersed phase at least 0.1% by weight of hydrophobic, dense discrete surface esterified silica particles. Since the liquefied hydrocarbon gas evaporates almost instantaneously the surfaces are coated with the esterified silica particles. The amount of silica deposited on the metal surfaces should provide a thin film.

The invention, while generally directed to improving the coefiicient of friction between surfaces that tend to move one with respect to the other, is particularly useful in treating railway car wheels and tracks, such as the driving wheels of diesel locomotives, to improve the frictional contact between the wheel and the rail. In laboratory experiments designed to duplicate the effect of railway car wheels moving on tracks, it has been shown that the compositions of the inventions are capable of being applied to moving surfaces and rapidly developing substantial increases in the coefiicient of friction between such surfaces. It is, therefore, possible now to provide to the railway industry frictionizing chemical materials which may be applied as needed to the driving wheels of diesel locomotives and the tracks upon which they run.

Thus, the compositions of the invention are capable of providing improved frictional effects whereby the railroad industry may increase the loads capable of being pulled by locomotives, thereby improving the operational efficiency and the cost of hauling large quantities of freight and passengers over railway right of ways.

THE LOWER ALIPHATIC LIQUIFIED HYDROCARBON GASES The lower aliphatic liquified hydrocarbon gases which form the liquid phase of the novel organo sols of the invention may be selected from a large number of wellknown lower aliphatic gaseous hydrocarbons. Illustrative are such gases as isobutylene, isobutane, n-butane, propylene, propane, liquified petroleum gas (LPG), acetylene, ethylene and the like. Also useful is liquified natural gas.

Gases of the type described may be combined to provide solvents for the esterified silicas. A very useful liquified mixture is composed of 85% of n-butane and of propane.

The above materials which are gaseous at room temperature may be liquified by known means. Illustrative would be the compression of such gases by using either cascade or series compression and cooling cycles. Also useful as a means for liquifying these gases is to reduce them in temperature to a point where they become liquid.

Since the gases described above are not liquid at room temperature it is necessary that they be stored in suitable pressurized or insulated containers whereby they are maintained in a state of liquefaction. Preferred gasses have a boiling point below 0 C. They all contain from 1 to 4 carbon atoms in an aliphatic chain.

THE SURFACE ESTERIFIED SILICAS The organo coated silicas which are dispersed as a sol in the liquified hydrocarbon gases are described in Iler, US. 2,801,185, the disclosure of which is incorporated herein by reference. These finely divided silicas comprise a hydrophobic, dense, discrete, surface esterified silica particles. They are esterified with a monohydric unsubstituted alcohol which is characterized as having the carbon atom attached to the alcohol oxygen being also attached to at least one hydrogen atom. The alcohols are further characterized as containing from 2-18 carbon atoms in cha le gth. The extent of surface esterification is sufficient to make the specific hydroxilated surface area of the particles being less than about 10 mF/g.

The particles of the esterified silica have an average particle size diameter within the range of 5-150 m and preferably an average particle size from about 10-60 mg. They are dispersed in the liquified hydrocarbon gas to provide from 0.1 to 70% SiO Preferred sols contain from 5 to 65% by weight SiO The finely divided hydrophobic silica powders described above may be conveniently prepared in accordance to the teachings of Mindick et al., US. 3,336,235, the disclosure of which is incorporated herein by reference. By using the techniques of Mindick, et a1. it is possible to pre pare organo coated surface esterified finely divided silica particles which are colloidally dispersable in the liquified hydrocarbon gases.

A preferred surface esterified silica powder which is surface coated with iso decanol is prepared in accordance with the following example:

EXAMPLE I Into a one liter, three-necked round bottom glass, equipped with stirring device, heating mantle, thermometer and a dropping funnel, was added 350 grams of a Cellosolve sol containing 35.5% silica colloidally dispersed in 2-ethoxy ethanol. To this was added 58.5 grams of mixed isomers of decyl alcohol. The distillation of Cellosolve" was then begun. During the replacement of Cellosolve, 275 grams of additional decyl alcohol and grams of dibutyl carbitol were added by means of the dropping funnel in incremental additions. A relatively constant volume in the flask was thereby maintained. During the replacement process, the temperature of the liquid rose from an initial temperature of l32 /2 C. to 190 C. over a period of three hours and 18 minutes. The temperature was raised for purpose of esterification. At 212 C. the liquid sol was then recovered and bottled with methanol overnight.

EXAMPLE II This example illustrates the ease of preparing solid surface-esterified silica particles directly from the sol product itself with a minimum of processing. One part of the liquid sol product, as synthesized above, was added slowly to approximately three parts by weight of metha- 1101 with agitation at room temperature in a Dopp kettle. During addition, a white precipitate was formed. After the sol product has been added, stirring was continued for an additional 10-15 minutes. Agitation was stopped and the precipitate allowed to settle for 1 to 1 /2 hours. The supernatant liquid contained methanol and excess iso decanol and dibutyl carbitol was decanted, leaving a heavy slurry of approximately 40% solids and liquids. This slurry was fed to a vacuum type drum filter and the wet solids solids, 35% moisture) were recovered at a rate of 50 lbs/sq. ft./hr. The wet cake was placed in trays and dried in a gravity feed oven at -170" F. The time required to dry this product to 0.5% volatiles was approximately 10-15 hours. The product was then ground and packaged for use.

Another preferred species of finely divided esterified silica are those esterified with 0x0 alcohols having the following composition:

Ingredient: Weight percent Octyl-alcohol 2-20 Nonyl-alcohol 5-40 Decyl and higher alcohols 25-90 EVALUATION OF THE INVENTION EXAMPLE III Eslcrilied silica was prepared in accordance with the procedure given in Example II.

Its solubility in various liquified hydrocarbon gases was determined by the following procedure:

A cylindrical tank containing a given hydrocarbon gas was placed in a large gallon bucket containing Dry Ice and acetone.

The contained gas was liquified as a result of its subjection to the low temperature, i.e. -70 C.

The liquified hydrocarbon gas was then poured into a 500 ml. Z-necked, round bottomed flask. This flask was immersed in an acetone-Dry Ice bath. The required low temperature for liquification was, therefore, sustained.

The referred to esterified silica Was then added in increments, accompanied by stirring, until saturation solubility occurred. Samples of these solutions were taken and placed on a pre-weighed watch glass. The weight of the sample was also determined.

Upon standing at room temperature, the liquified hydrocarbon gas eventually evaporated leaving the esterified silica behind. Solubility was then determined in terms of weight percent.

Solubility of the esterified silica in various liquified hydrocarbon gases is given below in Table I.

Table I illustrates that the iso decanol esterified silica is extremely soluble in n-butane and iso-butylene. It is less soluble in the other liquefied gases. When it is desired to use a particular liquified hydrocarbon gas as the continuous phase for the esterified silica it is possible to place on the silica surface an ester grouping which renders the silica particles dispersible to varying degrees. Thus, for example, it is sometimes desirable to use esterified silicas of lower aliphatic alcohols such as isopropanol or butanol when it is desired to disperse the colloidal silica particles in LPG or liquified natural gas.

EXAMPLE IV Evaluation of the effectiveness of different samples of pastes, powders and sprays for improving the coefficient of friction between locomotive wheels and their rails was accomplished through the use of the Amsler Friction Testing Machine.

The Amsler Friction Testing Machine 1 simulates locomotive wheel and rail conditions. It provides a quick and easy method for continuously measuring and recording the coeflicient of friction between test specimens in combined rolling and sliding contact.

Test specimens were repeatedly scrubbed with detergent and rinsed with warm water to remove all traces of oil. Hard black deposits of iron oxide were scraped off and the specimens were scrubbed and rinsed again. They were dried with a paper towel and put on the Amsler Friction Testing Machine without finger contact.

The Amsler Friction Testing Machine was started with the swing open. The pen was lowered and allowed to run with no load for about seconds to establish no load reference line. Swing was closed and a load of 92 pounds was applied. The test was allowed to run for three minutes or until there was no further increase in the co- Cl'l'lClBl'lt of friction reading. Tre highest steady reading was taken as the coefilcient for clean specimens.

ASTM bulletin September 1950, page 47, at subs. for a description of the Amsler Friction Testing Machine.

Under actual operating conditions oil on the rails or on the locomotive wheels causes high coefficients of friction more difficult to obtain. As a result, tests were conducted where the specimens were oiled.

After the specimens were in place, the machine was started with the swing open. Facial tissue wet with a drop of oil was used to apply a thin oil film to each specimen. Excess oil was removed by wiping the rotating specimens with a clean section of facial tissue. The swing was then closed, the load applied and allowed to run for 15 to 30 seconds to establish a coefiicient of friction for the oiled surface.

The desired treatment was then applied without stopping the machine.

Materials of various types and form were tested.

Tabulated results with clean specimens, oiled specimens and several different treatments are shown in Table II below.

1 Diluted as containing 15% SiOe.

From Table II it is obvious that the compositions of the invention are capable of rapidly increasing the coefiicient of friction between moving metal surfaces to a surprising degree. It is believed this result is achieved due to the rapid, and in some cases almost instantaneous, evaporation of the liquified hydrocarbon gas when exposed to normal atmospheric temperatures. Even with this rapid evaporation the esterified silica dispersed in the liquified hydrocarbon gases adheres to the metal surfaces, thereby allowing their frictional effectiveness to act upon the moving metal surfaces.

CONCLUSION The invention provides improved compositions which rapidly cause an increase in the coefficient of friction between two metal surfaces that tend to move one with respect to the other. The compositions of the invention provides a novel organo sol which has been heretofore unknown to the art. It is completely unexpected that surface esterified finely divided silica particles are colloidally dispersible in liquified hydrocarbon gases. Having thus described the invention it is claimed as follows.

What is claimed is:

1. The method of improving the coefficient of friction between contacting metal surfaces capable of moving one with respect to the other which comprises the steps of treating said surfaces with a silica organo sol, said organo sol having as its continuous phase a lower aliphatic liquified hydrocarbon gas which contains from 1 to 4 carbon atoms and mixtures thereof and as the dispersed phase at least 0.1% by weight of hydrophobic, dense, surface esterified silica particles having an average particle size of from 5 to millimicrons, the particles being surface esterified with a monohydric, unsubstituted alcohol wherein the carbon atom attached to the alcohol oxygen is also attached to at least one hydrogen and the alcohol molecule contains from 2 to 18 carbon atoms, and the extent of surface esterification being sufficient to make the specific hydroxylated surface area of the particles less than about 10 mP/g.

2. A method of improving the coeflicient of friction 0 between contacting metal surfaces capable of moving one with respect to the other which comprises treating said surfaces with a silica organo sol, said organo sol having as its continuous phase a liquified lower aliphatic hydrocarbon gas from the group consisting of liquified methane, ethane, ethylene, propane, propylene, butane, butylene, isobutane, isobutylene, acetylene liquified petroleum gas, liquidfied natural gas, and mixtures thereof and as its dispersed phase at least 1% by weight of hydrophobic, dense, surface esterified silica particles, the particles being surface esterified with a monohydric, unsubstituted alcohol wherein the carbon atom attached to the alcohol oxygen is also attached to at least one hydrogen and the alcohol molecule contains from 2 to 18 carbon atoms, and the extent of surface esterification being sufficient to make the specific hydroxylated surface area of the particles less than about 10 mP/g.

3. The method of claim 2 where the surface esterified silica particles have been surface esterified with an oxo alcohol having the following composition:

Ingredient: Weight percent Octyl-alcohol 2-20 Nonyl-alcohol -40 Decyl and higher alcohols 25-90 4. The method of claim 2 where the surface esterified silica particles thave been surface esterified with an iso decyl-alcohol.

5. A silica organo sol friction treatment composition comprising a liquified lower aliphatic hydrocarbon gas which contains from 1 to 4 carbon atoms and mixtures thereof having dispersed therein from 0.1% to about its saturation solubility, surface esterfied silica particles having an average size of 5 to 150 millicrons, the particles being surface esterified with a monohydric, unsubstituted alcohol wherein the carbon atom attached to the alcohol oxygen is also attached to at least one hydrogen and the Ingredient: Weight percent Octyl-alcohol 220 Nonyl-alcohol 540 Decyl and higher alcohols 25-90 8. The composition of claim 5 where the liquified hydrocarbon gas is a mixture of a butane and propane.

References Cited UNITED STATES PATENTS 3,351,561 7/1967 Albrecht et a1. 106--36 3,124,505 10/1964 Doyle 252305X 2,801,185 10/1957 Iler l06308X 2,787,968 9/1957 Luvisi 106-36X OTHER REFERENCES Ucon Hydrocarbon Blends, Propellants, Union Carbide, l 963 DONALD J. ARNOLD, Primary Examiner U.S.Cl. X.R. 

